Field of the Invention
The disclosed and claimed concept relates to a circuit breaker and, more specifically, to a circuit breaker operating mechanism that is structured to resist rebounding from an open, first configuration to a closed, second configuration.
Background Information
Electrical switching apparatus include, for example, circuit switching devices, circuit interrupters, such as circuit breakers, network protectors, contactors, motor starters, motor controllers, and other load controllers. Electrical switching apparatus such as circuit interrupters and, in particular, circuit breakers, are well known in the art. Circuit breakers are used to protect electrical circuitry from damage due to an over-current condition, such as an overload condition or a relatively high level short circuit or fault condition. Circuit breakers typically include a number of pairs of separable contacts, an operating mechanism, and a trip unit. The separable contacts move between on open, first configuration and a closed, second configuration. The separable contacts may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to an over-current condition. That is, a circuit breaker includes an operating mechanism and a trip unit. The operating mechanism is designed to rapidly open and close the separable contacts. The operating mechanism is structured to be latched and thereby maintain the contacts in a closed configuration. The trip unit is structured to detect over-current conditions. When an over-current condition is detected, the trip unit releases the operating mechanism latch thereby allowing biasing elements to bias the operating mechanism and contacts, to an open configuration.
Generally, a circuit breaker is assigned a size and a “withstand” value. The size of the circuit breaker is substantially related to the size of the circuit breaker housing assembly or frame. Generally, a withstand value at 10× rated current is typical, or desired, for molded case circuit breakers and miniature circuit breakers. Other classes of breaker, such as, but not limited to, power circuit breakers and medium voltage breakers, have a withstand value to equal their interruption rating. The circuit breaker withstand value involves a balance between blow-off forces generated by electric currents flowing in the breaker and contact forces generated on the movable conductor by the operating mechanism. Thus, as the rated current for a given frame size is increased, the withstand value should be increased a corresponding amount. This relationship is, however, limited by the size, shape, configuration, and material properties of the elements of the circuit breaker. That is, as the withstand value is increased, the components of the circuit breaker must become more robust. Typically, the size of the circuit breaker elements is increased so as to increase their strength. The size of the circuit breaker housing assembly, however, limits the increase in the size of the internal elements. That is, if the size of the circuit breaker frame or housing assembly is increased to accommodate the larger components, the circuit breaker could not be considered to be of a selected size.
There is, therefore, a need for a circuit breaker having a greater withstand value while maintaining the size of the circuit breaker housing assembly. There is a further need for an improved conductor assembly that may be incorporated into existing circuit breakers.